In a rectifier assembly disclosed in British Pat. No. 976,458, the diodes carrying the load current are arranged in pairs between two rails which are braced against each other and which also constitute electrical conductors. The electrical connection between the diodes and the rails is achieved by contact pressure. This arrangement has the disadvantage that two main diodes must be arranged one after the other in the axial direction of the alternator, so that a great deal of space is required. The cooling of these diodes is also difficult.